merge revision(s) r42456: [Backport #8101]

	* time.c (get_timeval, get_new_timeval): use rb_obj_class()
	  instead of CLASS_OF() because CLASS_OF() may return
	  a singleton class.


git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/branches/ruby_2_0_0@44844 b2dd03c8-39d4-4d8f-98ff-823fe69b080e